The present invention relates to an image processing system that compressively codes image signals and an image decoding apparatus that decodes compressively coded image signals.
Recently, surveillance cameras have become more common, and higher resolution, higher frame rates and more viewpoints have been required. However, higher resolution, higher frame rates and multiple viewpoints cause the amount of moving image data to remarkably increase, raising communication costs and storage costs.
To solve this problem, an image processing apparatus that performs image compression processing by detecting a specific region in which, for example, a “face” is displayed from a moving image as a region of interest (ROI) and allocating a large number of bits to the ROI has been proposed (see JP 2009-49979A, for example).
The image processing apparatus reduces a data amount by controlling parameters applied to a compression unit to decrease an information amount of regions other than the ROI, that is, background regions, below an information amount of the ROI using a function of the compression unit which sets parameters for controlling a code amount and video quality for each block.
However, there are cases in which such a parameter control function cannot be added later when the compression unit is configured as hardware.
Accordingly, there has been proposed an image coding apparatus that reduces an information amount of a background region by performing a filtering process using a low pass filter on the background region to remove information of high frequency components in order to decrease the information amount of the background region without depending on a compression unit (see JP H4-219089A, for example). This image coding apparatus limits generation of artifacts at block boundaries while decreasing an information amount of image signals through filtering by the low pass filter.